function IScroll_init(_opt){
	var opt={
		wrapper_selector:"#scroll_wrapper",
		tipUp_selector:".pullUp",
		tipDown_selector:".pullDown",
		active_cls:"active",
		//-----------------------------
		mouseWheel: true,
		scrollbars: true,
		probeType:3
	};
	$.extend(opt,_opt);
	var $pullDown= $(opt.wrapper_selector + " " +opt.tipDown_selector);
	var $pullUp= $(opt.wrapper_selector + " " +opt.tipDown_selector);
	var $wrapper= $(opt.wrapper_selector);
	opt.startY=-$pullDown.outerHeight();
	var myScroll = new IScroll(opt.wrapper_selector,opt);
	var $pullDown= $(opt.wrapper_selector + " " +opt.tipDown_selector);
	myScroll.on('scroll', function(){
		if(this.y>0){
			$pullDown.addClass(opt.active_cls);
		}
	});
	myScroll.on('scrollEnd', function(){
		var _this=this;
		if(this.y>opt.startY){
			this.scrollTo(0,opt.startY,300);
		}
		if($pullDown.hasClass(opt.active_cls)){
		}
		$pullDown.removeClass(opt.active_cls);
		$pullUp.removeClass(opt.active_cls);
	});
	document.addEventListener('touchmove', function (e) { e.preventDefault(); }, false);
	return myScroll;
}
$(function(){
	window.myscroll= IScroll_init();
	console.log(myscroll);
});

